There are now well established techniques for carrying out endoluminal treatments and diagnoses on a patient. A diagnosis may, for example, involve injection of contrast material and saline solution, A treatment may, for example, involve insertion and deployment of implants or prostheses for carrying out surgical procedures. It may also or in the alternative involve insertion, use and removal of catheters or tools, such as angioplasty or moulding balloons. A treatment may also involve injection of contrast material, saline solution, administration of medicaments and so on. The treatments and diagnoses can be effected within a patient's vascular system, such as arteries or veins. They can also be carried out within other bodily tubes which carry pressurized fluids, examples being the bilary tree and urological system, as well as within an organ, such as the cerebral ventricles and so on.
Endoluminal deployment or treatment devices typically include an elongate catheter assembly having an outer sheath and an internal dilator tip for insertion into the vasculature of a patient up to the deployment or treatment site and into which an elongate treatment or deployment element can be inserted. For example, the sheath may house a catheter or pusher element for carrying a medical device to be implanted into the patient. The sheath may also carry elongate tool elements, catheters for administering medicaments and so on. In the course of such treatments or diagnoses it is important to ensure that the patient does not suffer blood loss through the sheath. For this purpose, it is known to provide at the proximal end of the introducer one or more haemostatic valves in series to close off leakage through the outer sheath.
These haemostatic valves must be such that they allow sliding movement of any delivery or treatment element within the sheath and also for the removal and replacement of such elements. The latter is important, for example, in that many medical procedures may require a plurality of different elements to be passed through the sheath at different times of the procedure for location at a specific position in the patient. Normally, when an exchange of devices takes place, the haemostatic valve has both to seal and allow movement of devices with a diameter up to the inner diameter of the sheath, much smaller devices such as a guide wire typically of 1 mm or so, as well as to seal when the sheath is empty.
Typically, in any one assembly there is provided a variety of valves in light of the difficulties in achieving a reliable seal, all while providing for the removal and replacement of the inserted elements.
Some of these valves are in the form of a disk of elastomeric material located at a proximal end of the sheath and within which there is provided a cut, straight or more commonly Y-shaped, through which an element can be inserted so as to be located within the sheath. As such valves do not provide a complete seal when they hold an insert, typically allowing leakage between the slit and the insert, it is common to use a plurality of such valves disposed in series with one another. These are either at different angular rotations relative to one another or are of different designs, so that collectively they provide a reasonably reliable seal. Typically, there will also be provided one disc with a round hole, optimal for the most-used diameter of a device which passes through that particular sheath. The round disc will give a certain friction, depending upon the need for a forceful seal or to accommodate the size of the actual device passed therethrough.
Examples of such valves can be found, for instance, in U.S. Pat. No. 4,673,393, U.S. Pat. No. 5,176,652 and US-A-2005/017,479.
A difficulty arises with the use of a series of seals, however, in that in order to have good sealing characteristics they also tend to create a significant resistance to movement of an insert, which can substantially impair the operability of the insert by making it too hard to slide within the sheath. This can in some instances lead to damage of the insert, for example by kinking. This risk is particularly acute for inserts which are by necessity very flexible or of a small diameter.
In order to mitigate the above disadvantages, it is also known to use a haemostatic valve which can be opened and closed under the clinician's control. This has the advantage that an element can be inserted into the sheath and moved therealong with relative ease while the controllable haemostatic valve is in an open configuration. Once the insert is in place, the valve can be tightened to effect the seal. Such tightening is also advantageous during the procedure of insertion of the device in the sheath assembly. In practice, it is often necessary for such a structure also to include a valve which self-seals, such as one or more of the disk-shaped valves mentioned above, to ensure sealing during handling.
Such selectively openable and closable valve elements typically have an elongate valve member of tubular form which can be closed by twisting or by application of pressure laterally on the valve element by means of one or more movable closing plates.
Examples of such selectively sealable haemostatic valve assemblies can be found, for example, in U.S. Pat. No. 5,391,154 and U.S. Pat. No. 5,653,697.
A problem with such selectively sealable haemostatic valve assemblies is that they require an additional, controlled, operation to be performed by the clinician during the surgical procedure, that is the opening and closing of the valve element. This can be particularly disadvantageous during any medical procedure, where the clinician is typically required to perform several other tasks. If the valve is not properly closed, there is the risk of leakage of patient fluid through the assembly.
The applicant has previously proposed an improved haemostatic valve assembly, which is the subject of U.S. patent application Ser. No. 12/288,705. The assembly includes a chamber able to be pressurized, an elongate resiliently deformable valve element located within the chamber, a passage through which an elongate element can pass, the valve element being located so as to envelop at least a part of the passage, and means for supplying pressurized fluid to within the chamber, wherein pressurization of the chamber causes the valve element to be biased towards a closed position.
In practice the valve element is biased by the application of fluid pressure to a sealed configuration, at least when an element is located in the valve assembly. The advantage of the system is that the pressurized fluid can provide a reliable seal without requiring a large force to be applied to the seal and thus to any insert held within the valve element. In the case of a generally tubular valve element, the pressure applied to the valve can achieve reliable sealing both when the largest or the smallest inserts are placed therein as well as when any such insert is completely removed from the sheath and the chamber. Since the sealing force need not be large as a result of the substantially constant biasing force applied by the pressurized fluid, the force required to slide inserts through the closed or just sealing valve as it is closed towards the insert valve can be much less than with prior art devices. Furthermore, the pressure may be adjusted to provide an optimum seal at the various sizes of device in use at any particular moment. The source of pressurized fluid includes a syringe coupled to a port of the chamber, a drop bag or a Pressure supplied from the patient's blood stream.
In all of these examples, the chamber can be pressurized at the start of the medical procedure with no further intervention normally being required. Thus, not only can this valve assembly provide a better sealing arrangement but one which is also simpler to implement.